Spark plug



"nec, 16,1924.

. E. HUNT sARK PLUG I Filed Feb. 12, 1923 Patented Dec. 16, 1924.

UNITED STATES CLAYTON E. HUNT, OF CHARLOTTE, MICHIGAN.

SPARK PLUG.

Application filed February 12, 1323.

T all 'zo/mm it mory concern.'

Be it` known that I, CLAYTON E. HUNT, a citizen of the United States, residing at Charlotte, in the County of Eaton and State of Michigan, have invented certain new and useful Improvements in Spark Plugs; and l do hereby declare the following to be a full, clear, and exactdescription of the inventi on. such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a spark plug.

It is aimed to provide a generally improved, inexpensive leak-proof and substantially carbon-proof plug capable of ready disassembly for inspection and repair.

Another object is to provide a construction which is insulated in a novel manner as hereinafter disclosed so that it may avoid the usual frangible insulation.

Another object is to provide a construction in which the central electrode may have insulation wrapped around the same and held in place against unwrapping by additional insulation and parts of the plug.

Various additional objects and advantages will become apparent from aconsideration of the description following taken in connection with the accompanying drawing illustrating an operative embodiment.

In said drawing:- r

Figure 1 is a substantially central vertical sectional view through the improved plug,

Figure 2 is a bottom View,

Figure 3 is a cross sectional view on the line 3-3 of Figure 1,

Figure 4: is a cross sectional view on the line 4-41 of Figure l, and

Figure 5 is a detail perspective view of the bushing employed.

Like reference characters designate like or similar parts in the difi'erent views.

Cari-ying out the invention, an attaching shell lO of suitable metal is utilized which is adapted to be screwed or otherwise attached as at 1.1 into the cylinder head of an engine. It will be obvious that the shell may be of any suitable size or shape and with the screw threads 11 of any desired pitch, to adapt it to the cylinder head with which it is to be used.

A suitable nut 12 by means of screw threads at 13 on the same and on the shell 10, is fastened to the latter. Nut 12 is recessed at its lower surface as at 14 in order to accommodate a bushing 15 therein.

senin N o. 618,560.

Both the nut 12 and bushing 15 are preferabl y of metal. The diameter of the bushing 15 before application to the recess 14 'is oversize with respect to the diameter of recess 1.4 so that it will wedge snugly and tightly :in the recess 142. Such wedging action is permissible iu view of slits or slots which are provided at 16 longitudinally of the bushing 15 and extending alternately from 05 opposite edges thereof.

Shell 11 has an electrode 1'7 thereon to coact with the central electrode of the plug which is designated 18. The electrode 18 has a sheet of mica or other suitable insulation which is designated 19, wrapped about the same. Said electrode 18 and mica 19 pass snugly through central openings 20 in the nut 12 and the bushing 15. Thus the sheet of mica 19 cannot become unwrapped.

the bushing 15, a plurality of washers 22,

of insulating material, for instance mica, are interposed in tight and intimate engagement with each other to form an insulating body. Some of these washers 22 also extend around the sheet 19 at the portion thereof which projects below bushing 15.

The electrode 18 and sheet 19 also extend above the nut 12. Above said nut 12, a plurality of washers 23, for instance of mica or other insulating material surround the electrode 18 and insulation 19 form an insulating body and to prevent unwrapping of the insulation 19. A metal diskor cap 24 rests on, the uppermost washer 23. Electrode 18 extends above the cap 24 and has 1 a clamping nut 25 screw threaded thereon. Above nut 25 a binding nut 26 may be screw threaded so that as usual a wire or conductor may be clamped to the plug intermediate said washers 25 and 26. Shell 10 is usually grounded in the electric circuit as will be understood.

The plug constructed as described Will be substantially carbon-proof as it Will not leak and will produce a spark suificiently intense to burn the carbon at the spark gap practically as rapidly as it is produced. Also the method and means of providing the nonfrangible insulation is rapid and inexpensive. p

Various changes may be resorted to Within the spirit and scopeof the invention.

Having thus described the invention, What I claim is 2-' 1. A spark plug having a shell provided with an electrode, a nut threaded to said shell having its bore provided with an enlargement, an electrode to coact With said electrode passing through said bore, insulation wrapped about the second mentioned electrode and extending through the bore, and a bushing located in said enlargeinent surrounding and coinpressing said insulation against the second mentioned electrode.

2. l\ spark plug having a shell provided With an electrode, a nut threaded to said shell, said nut having a recess constituting an enlargement of its bore, a second electrode, said second electrode having insulation wrapped about the same and passing through said recess, an insulated bushing of oversize fitted in said recess and ex' rting an inward pressure against said i sulation, Washers of insulation surrounding said insulation and second electrode be OW the bushing, an abutment on the second electrode below the washers to coact therewith, \Vashers of insulat-ion about the first nientioned insulation and second electrode above the nut, and a nut on the second electrode above the last mentioned Washers.

In testimony whereof I .afiix my' signature in presence of two witnesses.

' CLAYTONE. HUNT. W'itnesses M. D. CRAWFORD, FRANCIS A. JADEL. 

